1. Field of the Invention
The present invention relates to an image display apparatus using an electron-emitting device.
2. Related Background Art
In a flat display in which: a large number of electron-emitting devices are arranged as electron sources on a flat substrate; a phosphor as an image forming member on an opposing substrate is irradiated with electron beams emitted from the electron sources; and the phosphor is allowed to emit light to display an image, the inside of a vacuum container including the electron sources and the image forming member must be kept at a high vacuum. When a gas is generated in the vacuum container to increase the pressure in the container, the increase adversely affects the electron sources to reduce an electron emission amount, thereby making it impossible to display a clear image, although the degree of the adverse effect varies depending on the kind of the gas.
In particular, the following problems are characteristic of a flat display. A gas generated from an image display member accumulates near an electron source before it reaches a getter placed outside an image display area, so a local increase in pressure and the deterioration of the electron source incidental to the local increase occur. Japanese Patent Application Laid-Open No. H09-82245 describes that a getter is arranged in an image display area to immediately adsorb a generated gas, thereby suppressing the deterioration and breakage of a device. Japanese Patent Application Laid-Open No. 2000-133136 describes a structure in which a non-evaporable getter is arranged in an image display area and an evaporable getter is arranged outside the image display area. Furthermore, Japanese Patent Application Laid-Open No. 2000-315458 proposes that a series of operations consisting of degassing, getter formation, and seal bonding (making a vacuum container) are performed in a vacuum chamber.
Getters are classified into an evaporable getter and a non-volatile getter. The evaporable getter shows an extremely large exhaust velocity with respect to water or oxygen. However, each of the evaporable getter and the non-evaporable getter shows an exhaust velocity close to zero with respect to an inert gas such as argon (Ar). An argon gas is ionized by an electron beam to generate a plus ion. The plus ion is accelerated in an electric field for accelerating an electron to be bombarded with an electron source, thereby damaging the electron source. Furthermore, the argon ion may cause discharge inside an apparatus to break the apparatus.
Japanese Patent Application Laid-Open No. H05-121012 describes a method, as an exhausting means for exhausting an inert gas, involving connecting a sputter ion pump to a vacuum container of a flat display to maintain a high vacuum for a long period of time.
As shown in FIG. 9, in the flat panel display, a face plate 109 having a phosphor film and a container main body are hermetically sealed with a sealing material to constitute a vacuum container. An electrode structure is arranged in the container main body and has a field emission cathode, and an electron beam emitted from the cathode is modulated by an inner electrode, that is a modulation electrode to be directed toward the phosphor film for graphic display. An ion pump for maintaining a vacuum is joined to the container main body. In an embodiment of the ion pump, for example, 1,000 gauss (0.1 tesla, hereinafter, the unit “tesla” for a magnetic flux density is indicated by T) is applied by a magnet 121.
However, in the structure in which the ion pump is connected to the vacuum container via a metal seal such as an ICE flange, a heavy metal seal made of a metal material is locally placed on one side of the flat panel display. Moreover, the magnet is directly attached to an ion pump container 120 without any yoke, so the resultant weight is large. Accordingly, in joining the ion pump and the metal seal to the container main body, there arises inconvenience such as the deformation or breakage of a portion at which the metal seal is attached to the container main body. As a result, an event that the vacuum container leaks often occurs, with the result that a production yield reduces.
In addition, noise occurring when discharge occurs inside the ion pump may disturb an image of an image display apparatus.